Exchangers of this type, which are constituted from a sheet of bent plate which is coiled on itself about the bend are known. In the course of the phase of coiling, spacer elements are arranged between the different spiral plates of the exchanger, intended to space the plates apart from one another so as to allow a flow of fluid between these various spiral plates. The end of the exchanger as well as the edges of the sheets forming the spiral plates must consequently be obturated, this usually being effected by welding beads. Such an exchanger is thus constituted by two independent circuits in which fluids, and in particular liquids, can circulate, namely, on the one hand, the space included between the various spiral plates and, on the other hand, the space included between the two bent walls of each spiral plate.
Although such an exchanger is quite satisfactory as far as its functioning is concerned, it presents drawbacks regarding its mode of manufacture and, more specifically regarding the production of the two welding beads intended to join the edges of the two sheets of plate forming the spiral plates. In effect, the shape of these welding beads is particularly complex as they must follow the spiral shape of the plates. This welding operation therefore constitutes a difficult operation which must thus be carried out by manual means.